Reusable UI components in React - Step-by-Step Execution

Concept Flow - Reusable UI components

Define Component

↓

Use Component in JSX

↓

React renders Component

↓

Component returns UI elements

↓

UI appears on screen

↓

Component can be reused multiple times

This flow shows how a reusable React component is defined, used in JSX, rendered by React, and displayed on the screen multiple times.

Execution Sample

React

function Button({ label }) {
  return <button>{label}</button>;
}

function App() {
  return <>
    <Button label="Save" />
    <Button label="Cancel" />
  </>;
}

Defines a Button component that shows a label, then uses it twice with different labels.

Execution Table

Step	Action	Component	Props	Rendered Output
1	Define Button component	Button	{ label }	Returns <button>{label}</button>
2	Define App component	App	none	Returns two Button components with labels 'Save' and 'Cancel'
3	Render App	App	none	React calls App, which returns two Button elements
4	Render first Button	Button	{ label: 'Save' }	<button>Save</button> appears on screen
5	Render second Button	Button	{ label: 'Cancel' }	<button>Cancel</button> appears on screen
6	Display UI	App	none	Two buttons labeled 'Save' and 'Cancel' visible
7	Reuse possible	Button	any label	Can create more buttons with different labels
8	Exit	none	none	Rendering complete, UI ready

💡 All components rendered and UI displayed; reusable components can be used again with different props.

Variable Tracker

Variable	Start	After Step 4	After Step 5	Final
label (first Button)	undefined	"Save"	"Save"	"Save"
label (second Button)	undefined	undefined	"Cancel"	"Cancel"

Key Moments - 2 Insights

Why do both buttons show different labels even though they use the same Button component?

Because each Button instance receives different props (label) as shown in execution_table steps 4 and 5, React renders them with their own label.

Does defining the Button component multiple times create multiple copies?

No, the Button component is defined once (step 1). React reuses this definition to render multiple instances with different props (steps 4 and 5).

Visual Quiz - 3 Questions

Look at the execution table, what label prop does the Button component receive at step 5?

A "Cancel"

B undefined

C "Save"

D "Submit"

💡 Hint

Check the Props column at step 5 in the execution_table.

At which step does React render the first Button component?

A Step 3

B Step 4

C Step 5

D Step 6

💡 Hint

Look for the step where the first Button with label 'Save' is rendered.

If you add another <Button label="Delete" /> in App, what changes in the execution table?

A Step 4 label changes to 'Delete'

B No change, because Button is reusable

C A new step rendering Button with label 'Delete' is added after step 5

D App component definition changes

💡 Hint

Adding a new Button means React renders one more Button instance, so a new rendering step appears.

Concept Snapshot

Reusable UI components in React:
- Define a function component that accepts props.
- Use the component in JSX with different props.
- React renders each instance separately.
- Components can be reused anywhere with different data.
- This keeps UI code clean and consistent.

Full Transcript

Reusable UI components in React let you write a component once and use it many times with different data. You define a component as a function that takes props and returns UI elements. When you use this component in JSX, React renders each instance with the props you give it. For example, a Button component can be used twice with labels 'Save' and 'Cancel'. React calls the Button function twice with different props and shows two buttons on screen. This approach saves time and keeps your UI consistent and easy to maintain.